An electrostatic lens, operated in accel–decel mode, is presented. The lens has advantage of low chromatic aberration, which is about2/3the amount produced by a conventional einzel lens operated in decel mode. The lens has two pieces of electrodes built in to accelerate and decelerate the beam. The decelerating electrode works as a main lens, while the accelerating electrode enhances the beam energy, reducing the aberration. Calculations for the accel–decel lens provideCcof 22 mm andfof 10 mm with working distance of 5 mm. The lens is suitable for producing a fine beam with a smaller spot size and with energy of over a few tens of kiloelectron volts. When the lens is applied to a 30 keV focused ion beam with 1 pA current, the spot size is estimated as 4.8 nm in diameter on a target with the above working distance.